This application is based upon and claims benefit of priority of Japanese Patent Application No. 2001-364152 filed on Nov. 29, 2001, the content of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a fuel injection pump having an one-way valve for supplying fuel into a pressurizing chamber and to a method of assembling the one-way valve.
2. Description of Related Art
A fuel injection system including a common rail and an injection pump for supplying pressurized fuel into an internal combustion engine is known hitherto. The fuel injection pump pressurizes fuel in a pressurizing chamber according to rotation of its driving shaft. Fuel pressurized to a predetermined level is sent out to the common rail from the pressurizing chamber. The injection pump includes a one-way valve that allows fuel to flow into the pressurizing chamber from a fuel tank while preventing fuel from flowing back into the fuel tank.
An example of a conventional one-way valve used in the fuel injection pump is shown in FIGS. 7A and 7B. A spring 102 is disposed between a valve body 101 and a valve member 100. The one-way valve is closed when the valve member 100 seats on a valve seat 103 formed on the valve body 101. The spring 102 biases the valve member 100 in a direction to close the one-way valve. To support the biasing spring 102 between the valve body 101 and the valve member 100, a ring-shaped washer 104 is provided at an upper end of the valve member 100. The upward movement of the washer 104 is restricted by an E-shaped ring 105 which is fixed to the valve member 100. Alternatively, the upward movement of the washer 104 is restricted by a stopper press-fitted to the valve member 100.
In a process of assembling the conventional one-way valve, the E-shaped ring 105 or the stopper has to be fixed to the valve member 100. Accordingly, a certain time is required in the assembling process for fixing the E-shaped ring 105 or the stopper. A contacting area between the E-shaped ring 105 and the valve member 100 is small as shown in FIG. 7B, and the biasing force of the spring 102 has to be received by the small contacting area. Therefore, the contacting area between the E-shaped ring 105 and the valve member 100, including portion where the washer 104 contacts the E-shaped ring 105, tends to wear due to abrasion during a long time operation of the one-way valve.
The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an improved one-way valve in which the abrasion wear is suppressed. Another object of the present invention is to provide an improved process of assembling the one-way valve.
A fuel injection pump driven by an automotive engine pressurizes low pressure fuel led from a fuel tank and sends out pressurized fuel to a common rail. The pressurized fuel accumulated in the common rail is injected form fuel injectors into the engine in a controlled manner. A one-way valve that allows fuel to flow only in one direction is installed in the fuel injection pump. The low pressure fuel led from the fuel tank flows into a pressurizing chamber in the fuel injection pump through the one-way valve. The pressurized fuel is prevented from flowing back by the one-way valve. The pressurized fuel is sent out to an outlet passage connected to the common rail.
The one-way valve is composed of a valve body, a valve member slidably coupled with the valve body, a biasing member such as a coil spring biasing the valve body in a direction to close the one-way valve, and a supporting member coupled to the valve member for supporting the biasing member between the valve body and the supporting member. The valve member is substantially rod-shaped and includes a head portion and a neck portion connected to the head portion, both of which serve to couple the supporting member to one end of the valve member. The supporting member is substantially disc-shaped. A through-hole and a groove, crossing each other, are formed in the supporting member.
In assembling the one-way valve, the valve member is slidably coupled to the valve body, and then a cylindrical portion of the valve member is inserted into the biasing member. Then, the head portion of the valve member is inserted into the through-hole of the supporting member, and the supporting member is further pushed down against the biasing member, so that the head portion is separated from the through-hole and the neck portion is positioned in the through-hole. Then, the supporting member is rotated relative to the valve member so that the groove formed on the supporting member is aligned to the head portion of the valve member. Because the neck portion is made smaller than the through-hole, the neck portion is freely rotatable in the through-hole. Then, the force pushing down the supporting member against the biasing member is released thereby to engage the head portion with the groove. The head portion is retained in the groove, while the biasing force being applied between the valve member and the valve body. Thus, the process of assembling the one-way valve is completed.
According to the present invention, abrasion wear in the one-way valve is suppressed because the biasing force of the spring is received by the supporting member having a wide surface. The assembling process of the one-way valve is simplified because the supporting member and the valve member are coupled to each other without using a mechanical connection such as staking.
Other objects and features of the present invention will become more readily apparent from a better understanding of the preferred embodiment described below with reference to the following drawings.